The metalorganic chemical vapor deposition system (MOCVD) allows for the growth of ultrathin epitaxial layers of III-V semiconductor compounds. This vapor deposition process is well suited for the growth of high performance semiconductor laser structures. Experimental data have been collected on a variety of MOCVD grown laser structures and are presented along with device design criteria.An important objective of this work has been to develop laser structures which can easily be designed to operate at a specified wavelength, and at the same time exhibit low threshold current, efficient operation. Two basic laser structures have been studied for these purposes, the alloy active layer double heterostructure laser and the graded barrier quantum-well laser. The optimization and characterization of these structures are discussed in depth. Very low threshold, high efficiency, high T(,0) laser devices have been obtained with the graded barrier quantum-well structure. In addition, several types of anomalous behavior have been observed in this structure, which do not occur in thicker active layer devices.A large fraction of this work is concerned with the design of laser structures which have desirable and controllable optical mode properties. Data is presented on both gain-guided and index-guided devices. High performance index-guided lasers have been developed using a new complementary self-aligned growth technique. In contrast with conventional self-aligned lasers, the complementary self-aligned laser is easy to fabricate and more versatile from the standpoint of the type of underlying laser structure which can be utilized. Low threshold current index-guided complementary self-aligned lasers have been fabricated using the graded barrier quantum-well active layer. These devices have stabilized fundamental lateral and transverse mode operations, and single longitudinal mode operation under cw conditions, with emission wavelengths ranging from 0.82 (mu)m to 0.695 (mu)m.In order to obtain higher output power levels, while maintaining stabilized optical modes, multiple emitter array structures have been studied. Experimental data on both gain-guided and index-guided array structures are presented.